① Positive number+positive number = positive number
② Negative number+negative number = negative number
The absolute value of a positive number is greater than that of a negative number. Then:
③ Positive number+negative number = positive number
The absolute value of a positive number is less than that of a negative number. Then:
④ Positive number+negative number = negative number
Subtraction:
① positive number (large)-positive number (small) = positive number
② Positive number (small)-positive number (large) = negative number
③ Positive number-negative number = positive number
④ Negative number-positive number = negative number
⑤ Negative number (large absolute value)-Negative number (small absolute value) = negative number
6. Negative number (small absolute value)-negative number (large absolute value) = positive number.
Note: the absolute value is to change the symbol in front of this number into a plus sign.